The ESBWR uses natural circulation with no recirculation pumps or their associated piping.
The passively safe characteristics are mainly based on isolation condensers, which are heat exchangers that take steam from the vessel (isolation condensers, IC) or the containment (passive containment cooling system, PCCS), condense the steam, transfer the heat to a water pool, and introduce the water into the vessel again.
This is also based on the gravity driven cooling system (GDCS), which are pools above the vessel. When very low water level is detected in the reactor, the depressurization system opens several very large valves to reduce vessel pressure and finally to allow these GDCS pools to re-flood the vessel.
The core is made shorter than conventional BWR plants in an effort to reduce the pressure drop over the fuel, thereby enabling natural circulation. There are 1132 bundles and the thermal power is 4500 MWth (1550 MWe).
Below the vessel, there is a piping structure which allows for cooling of the core during a very severe accident. These pipes divide the molten core and cool it with water flowing through the piping.
The probability of radioactivity release to the atmosphere is several orders of magnitude lower than conventional nuclear power plants, and the building cost is 60-70% of other light water reactors.
The energy production cost is lower than other plants due to:
General Electric has recalculated maximum core damage frequencies per year per plant for its nuclear power plant designs:
NRC ISSUES PROPOSED RULE ABOUT CERTIFICATION OF ECONOMIC SIMPLIFIED BOILING-WATER REACTOR STANDARD PLANT DESIGN
Mar 25, 2011; WASHINGTON, March 25 -- Nuclear Regulatory Commission has issued a proposed rule called: ESBWR Design Certification. The proposed...